The invention relates to an engaging and disengaging support element, in particular for a finger lever of a valve drive of an internal combustion engine. The support element includes a hollow cylindrical housing arranged with a first facing side in a receptacle of a cylinder head, whereby in the bore of the housing an axially movable inner element travels, which is spring-loaded against the housing via at least one compression spring. The inner element includes a head that projects beyond a second facing side of the housing, and the finger lever can be set on this head. The housing and the inner element each have at least one bore hole. These bore holes are aligned with each other in an axial displacement of the inner element to a furthest position from the first facing side, where in at least one of the bore holes, a coupling piston runs, which can be displaced sectionally into the other bore hole so that the inner element is connected to the housing.
A support element of this type is known from WO 95/16851, FIG. 5, which is considered to be the generic concept. This has an inherent disadvantage that it is built relatively high. As the expert can gather from the figure, there is a considerable space requirement due to the compression spring being positioned below the inner element. Should a support element of this type, for example, be implemented in existing engine designs, then construction space problems could result because of its relatively large height. Also, it is often not possible to drill the receptacle deeper for the support element in the cylinder head, since it would enter into the area, for example, for intake, outlet or cooling channels or the like.
The object of the invention is thus to create a support element of the type described above in which the cited disadvantages can be eliminated with simple mechanisms.
This object is achieved according to the invention in that the compression spring, at least for the most part, completely concentrically surrounds the inner element.
By this xe2x80x9cnestedxe2x80x9d construction method, considerable building space can be gained in the axial direction. In the present practice, this means a building space gain of 10 to 20 millimeters. The support element proposed according to the invention can thus for the most part be integrated afterwards into existing engine designs. Costly changes to the base design are therefore unnecessary.
An especially thin-walled construction of the essential structural parts of the support element is proposed. Due to this, it has on the one hand, only a very small weight. On the other hand, it has a relatively small width.
In realizing the invention, it is proposed to place the compression spring on one end against a spring plate in the area of the head of the support element, and on the other end, to let it act against a separate ring support, which is attached to the housing on the outside. Thus, the compression spring advantageously encloses, also partially, an outer sheath of the housing. As a compression spring, mainly a screw type and namely, a spiral spring, come into consideration. It is also conceivable that several compression springs that are nested into each other can be used.
The spring plate should preferably be manufactured as a thin-walled sheet metal part, for which only small manufacturing costs are necessary. It is furthermore provided that this spring plate is guided on its outer edge in the receptacle of the cylinder head. By this guide and also by the guide of the ring support radially outwardly in a corresponding receptacle of the cylinder head, the transverse forces introduced by the finger lever into the pressure piston can be efficiently transmitted and supported. The finger lever according to the invention has, for this purpose, a sufficient guide length in the cylinder head.
An especially advantageous embodiment of the guide for the spring plate is the object of an additional claim. According to the claim, the spring plate should make a transition on its outer edge into a ring collar, which passes directly in the corresponding receptacle. The ring collar can extend, depending on the constructive embodiment of the support element, in the direction to the receptacle or away from it. In addition, it can have a T-profile.
It is also proposed to construct the ring collar as a single piece with the pressure piston. For this, manufacturing processes such as metal powder injection molding and the like are suitable. It is, however, also proposed according to the invention to firmly affix the ring collar or the ring support using a connection method that is known, such as welding, soldering, clipping, snapping or pressing it in or onto the inner element or the housing. Also, separate elements, such as, for example, securing rings for affixing the position can be provided.
In particular for the case that the support element according to the invention should be installed into an aluminum cylinder head, it is proposed in making the invention more defined to provide the receptacle in the area of the outer edge of the spring plate with suitable wear protection methods. Here in particular, a separate and wear-proof insert piece such as a ring is considered, which however, can also be made to provide the receiving area, for example, with a separate wear protection layer, among other things.
Preferably, the structural parts of the inner element, housing, spring plate, and ring support, or at least one of these structural parts, should be made from a deep-drawn sheet metal material or an otherwise thin-walled metal material or lightweight material manufactured by a non-cutting process. These measures have an excellent effect on the manufacturing costs and reduce the mass of the support element as mentioned. In this manner, the ring support can be positioned at a height of the hole in the housing for the coupling piston. Thus, the ring support can be used as a radial extension of the bore of the housing for the coupling piston.
It is proposed that the coupling piston extends completely in the bore of the inner element in its uncoupled position and when coupled, can be displaced sectionally into the bore of the housing, and thus also into the connection bore of the ring support. Of course, a solution is also provided in which the piston runs radially outwardly in the bore of the housing during uncoupling and during coupling, and it can be displaced sectionally radially inwardly into the bore of the inner element. This shift occurs in a known way in at least one extension direction via a hydraulic medium. Preferably, a return movement against the hydraulic medium pressure can be managed via the compression spring force.
An especially preferred embodiment of the invention results if a hydraulic play compensation element is integrated into the inner element. This play compensation element is positioned axially above the bore for the coupling piston and has a preferably separately constructed path to the supply of hydraulic medium compared to the path for the supply of hydraulic medium to the coupling piston.
Included in the protective scope of the invention is also a solution in which the finger lever is set in bearings on the housing, and the inner element arranged in the housing is supported against the cylinder head.